Depolymerized copal-like resinous esters



May 31, 1949..

w. KRUMBHAAR 2,471,629

DEPOLYMERIZED COPAL-LIKE RESINOUS ESTERS Filed May 1, 1946 2 mix/Z7 ldloyere /d00/7IA Key l l I /I I8 21 26 4 If ammo/whom ,a1m v 7 1- r 2,411, 2

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s aww l This invention reiates'to synthetic resins, and resins which bedenominatedas copal-type 4 particularly, to synthetic copal-like resinous mthetic resins because they combine the feaesters, that is, synthetic resins which exhibit tures' of both natural and synthetic resins, parproperties of the processed fossil and to' I ticularly desirable features of the fossil gums. methods of. producing such copal-like' resinous 5 The inost important copal-like property, as esters as well as their utilization for various compared to the properties of orthodox synthetic purposes. resins of the same melting point and viscosity,

A consideration of the merits of synthetic is the high degree of solubility, molecularhomoresins as compared with natural willshow 1 geneity, mechanical toughness and heat stability. the background of the present invention; The ,Still further objects and advantages of the technical merits of high melting synthetic resins -present invention will appear from the more deor the group of modified phenolics, maleics,-and I tailed description'set forth .below, it being unhard resinous esters as compared tonatural gum derstood that this more detailed description is copalsare fairly obvious. These resins are progiven by; way of illustration and explanation duced under controlled conditions, yielding unionly, and not by way of limitation, since various form standardized properties 'and'fltting detailed changes therein maybe made by those skilled specifications and are produced in condition in the art, without departing from the scope and ready for combination with oils. spirit of the present invention.

Natural copals, on the other hand. are formed i In accordance with that more detailed deunder a variety of conditions as created'by nascription, there is shown in the accompanying ture, yielding resins of indistinctly deiined and drawing a graph illustrating the change in visfluctuating properties, containing water or aque-i cosity and -n'10lecular weight during processing ous solutions in various degrees of dispersion, 'of materials in accordance with the present and considerable quantities 'of foreign matter. invention. I Gum copals are not ready for direct use in var- In; accordance with th present invention a nish making; for this purpose 'they have to be newclass of resins is produced that may be derendered oil soluble by the cumbersome-process 1 nominated copal-type or copal-like synthetic of eopal running. resins or-resinous esters. Such novel products In spite. ofthese obvious drawbacks, the -naare produced by carrying out resiniflcation retm-al gums have retained great practical. 1 30. actions under certain limiting conditions to portance because certain valuable properties are build up large molecular aggregates which is more pronounced in natural gums after they then followed bymolecular degradation or dehave been depolymerized than in synthetic polymerization under controlled conditions. resins, For instance, copal ester varnishes have jI'he resins which can be subjected to the dehigher viscosity, better bodying and drying prop- 85 polymerization process are phenolic resins, parerties, greater toughness and 'durability'of the ticularly of the phenol formaldehyde. type, dried film, than rosin ester varnishes, all other maleic resins, particularly of the polyhydric alconditions being equal. Compared to modified cOhOI-pOIy c yp nd h resinous phenolics, copals are reputed to produce glossier t r of glyeerine 01 the pentaerythritcls. 'I'he= varnishes with less tendency to blooming. Copals 40 composition of such resins may vary in type and are also considered to cause better adhesion in uantity of ingredients, the deciding requirement varnishes, especially when the latter are baked being their ability to form a gelatinous resin on on metal. When copal varnishes are compared heating, which onfurther heating can be liqueto maleic resin varnishes, it is admitted that their fled again.

dried films are dark in the beginning, but it is ,-The building up of large molecular aggregates emphasized that they soon bleach out, and it is from small units is a familiar process in the stressed that copal varnishes under otherwise manufacture of phenolics and maleics, and high equal conditions are superior in rubbin and molecular rosin esters. If in these resins, either wearing characteristics. the phenolic or the maleic component exceeds a Among the objects of the present invention ,is 59 certainpe'rcehtage, or if more than a 'certain the production of a new type of resin or group amount 001131 is incflrpomted n the r in of resins which unite the advantages of both nars. the resin starts to gelatini n 3? tuna! and synthetic resins and eliminate their reconverts into an infusible and insoluble mass spectiv weaknesses during the course. of reaction, which is highly Further objects include the production of such xb h rm nd diificult to control. The final product cannot be liquefied or solubilized again.

Resin gels of such irreversible gel-type are un-- suitable for the production of copal-like resinous esters in accordance withthe present invention.

The resin gels treated in accordance with the present invention are reversible gels, i. e., gelatinous resins, which can be reconverted into fusible and soluble materials by suitablemethods. It is true that in certain resin making procedures, which are known in the art, depolymerization inherently or necessarily results. However, this invention uses depolymerization in a systematic and controlled manner by proper selection of a specific resinous material, a special heating and cooling cycle and an especially designed equipment and machinery.

The most important requirement as to chemical composition in the resin gels produced in accordance with the present invention for subsequent treatment, is the presence of free hydroxyl groups. The incorporation of such free hydroxyl groups into th molecule of the resingels may be accomplished in various ways.

One of the simplest methods of introducing hygdroxyl groups consists'in using an excess of glycerine during the process of making the resin, which glycerine exerts a pronounced degelling effect by partial alcoholysis. Other higher polybasic alcohols, including mannitol and sorbitol, may be used under proper circumstances to exert a similar effect. The pentaerythritol type alcohols, including the polypentaerythritols, are particularly useful and occupy a special position, because the hydroxy rosin esters of pentaerythritol have the peculiar property of acquiring exceptionally high viscosities before they actually gelatinize.

In this connection, special reference is made to my two U. S. Patents Nos. 2,268,946, entitled Phenol modified ethers, patented January 6, 1942, and 2,268,947, entitled Phenol modified esters, patented January 6, 1942, and furthermore, to my copending application, Serial No. 588,237, filed April 13, 1945, now U. 8. Patent 2,434,168, entitled Polyhydric polymer.

All three references describe methods of incorporating free alcoholic hydroxyl groups into synthetic resins.

Another way of introducing alcoholic hydroxyl groups is by the use of solubilized natural copals which have been made soluble by mastication. Ii. masticated natural gums are processed together with acidic rosin prdducts or synthetic resins, they often act very similar to polyhydric alcohols, supplying good evidence that they contain free alcoholic hydroxyl groups. The amount of masticated or soluble copal that can be incorporated depends upon its degree of solubilization and usually does not exceed 25% of the total resin. The process of solubilizing copal gums is described in my three U. S. Patents Nos. 2,007,333, entitled Method of treating natural gums and product resulting therefrom, patented July 9, 1935; 2,101,398, entitled Shellac substitute and process of producing the same, patented December 7, 1937, and 2,110,803, entitled Resinous products and process of making same, patented March 8, 1938. Mastication does not utilize heat to make the copals compatible with synthetic resins, but depends on mechanical force to achieve that purpose. I

In addition to free hydroxyl groups, the presence of fluxing and peptizing agents is desirable, in order to support the depolymerization process. Materials usable as fluxing agents are illustrated 4 by permanently fusible resins, such as rosin glycerine or pentaerythritol esters, coumarone resin. low melting rosin modified phenolic or maleic resins. These fluxing materials ease the fusion, and at the same time prevent local overheating and charring during the selling and degelling cycle. They also may enter the process chemically, forming mixed esters by interchange reactions with the substances whose depolymerization they have assisted as fluxing materials.

A further aid in the degradation of reversible resin gels are peptizing agents, as they are well known in colloid chemistry. Peptizers are required only in small amounts. It is not necessary to make additions of them in the present case,

' because decomposition products acting as peptizers, are formed during-the process and are not removed from the resin until degelling sets in. Such peptizing agents have the ability to penetrate into the gelled particles, to break them up into smaller units, and to disperse them within the liquid portion of the surrounding medium.

The above considerations illustrate the nature of the resin material treated in accordance with the present invention but certain factors of manufacturing procedure are important in carrying out the production of the copal-like resinous esters of the present invention. The building up of large molecular aggregates and subsequently breaking them down again 'into smaller units, requires special equipment and machinery. The heating equipment must be suitable to put in large amounts of heat, within short periods of time,

,and within high temperature ranges, and a very the heated resin is in the process of gelatinizing.

Thorough mechanical mixing is of the greatest importance at this stage of the process in order to equalize the temperature within the kettle to avoid decomposition, partial over-polymerization, and possible charring or even burning. Strong foam breakers are necessary to handle the heavy foaming which accompanies the processing. The maximum temperature to be reached depends upon the temperature at which the particular resinous ester gelatinizes, and generally should be from 20 to 40 0. higher than the gelation temperature. As a general rule with the majority of materials treated in accordance with the present invention, the peak temperature reached during the processing varies between 270 and 325 0., or more particularly 290 and 325 C., the temperature being stated approximately. So that in carrying out the treatment cycle, it is desirable to carry the heating and cooling through the region of gelation as rapidly as possible from just below the gelation temperature to the maximum temperature reached and return from such maximum temperature to just below the gelation temperature under the conditions of agitation and rapid heating as set forth above, depending to some extent on the nature of the materials being treated, the products to be obtained, and the equipment available.

In the early stages of the process of depolymerization, pressure may be applied and the heating carried out under such pressure to keep acid for example,by a decreasing viscosity of the kettle content after the maximum viscosity has been reached, the pressure is released. Finally vacuum may be applied to remove volatile matter present.

when the finished products are unloaded from the kettle, a decided copal-like odor as-obtained during Congo copal running is often noticed. obviously an odor produced by the degradation oi highly polymerized material. As in copal runnin the depoiymerization process in the manuiacture of copal-type synthetics is accompanied by a considerable loss of weight.

bility is directlyproportionai to melting point and viscosity tor the same resin "group. The process of the invention makes it possible to vastly increase solubility without decreasing melting point or viscosity, which is a greattechnical advantage.

The internal structure or the second sample is basically diflerentirom that of the first sample. The resin before the treatment of this invention does not give complete solutions even in strong solvents, but segregatesinsoluble or swelling particles, which can be separated irom the bulk of the solution by titration. Ai'ter the resin has To explain further the interesting new principles of producing copa'l-like synthetic resins, un-

der the present invention, two typical cases are The following tabulation registers acid values,

melting points, viscosities, and solubilities of samples taken from a production batch after diflerent times of processing, and at-variousbatch temperatures. The viscosity is expressed by wayoi the Gardner scale as that of a 60% resin solutionin xylol. The solubility is given as number of cc;

in titrating to cloud point 10 grams of a 60%:

resin solution in xylol with mineral spirits. It is also given as the temperature at which a clear solution is obtained, when the resin is heated up with two parts of Zbodylinseed oil.

passed through the degeliingprocess, it dissolves completely even in weaksolvents, indicating the absence of any overpolymerized parts. The fact that in spite of this the viscosity oi the two samples is alike, proves that low-molecular portions have increased, leading to a higher de ree of molecular homogeneity.

- :The process of the invention also produces resins of higher bodying speeds, as cambe proved by comparing the two resin samples in question. For this purpose, one part of the resin is heated up with two parts of Z bodied linseed oil to 300 0., and held there until a viscosity of H is reached. when a sample is thinned with an equal amount of mineral spirits. The time necessary to attain'this viscosiiyis the bodying time; it amounts to 100 minutes for the untreated material and to only 70 minutes tor the new resin. The reason. for the increased bodyins time is mainly due to the fact that no time is lost for degelling of the treated resin, whereas the old material requires considerable time iordestroyin the falsebody orits overpolymerized parts.

when the two samples taken after 18 and 33 hours respectively, are compared for heat stability, a substantial diflerenceappears which-is of great economical importance, because heat losses Solubility 'rem tum .Time of {Acid Mel fiff mowing value Viscosity c Oonditionolbetch g Temperature D as Hours Degrees Degree:

240 so 142. o so 200 Liquid.

200 is. as 145 U is 210 Do.

280 34 is 145 U 24 mo Liquid.

It will be seen that the peak of gelation process in the particular case given is reached between 25 and hours of treatment, when the melting point is at its highest and the solubility isat its lowest level. The above tabulation serves well to define the character of the new material, particularly by comparing the sample taken after 18 hours of treatment with the sample taken after 33 hours of treatment, the first one representing the old type of resin, the second one being the new type of material. Both samples are taken froma liquid batch, both have the same melting point, the same viscosity, and outwardly look exactly alike. However, due to the fact that the material of the second sample has passed through the process of gelation and degelling, it has acquired entire diflerent properties;

Its solubility is greatly improved both in volatile solvents and oil. Expressed in cc. of mineral spirits titration, it has increased 60% in volatile solvents. In drying-oil it has improved to the extent that the point of clarification in'bodiied linincrease the vmaterialvcosts. The determination iscarried out simply by heating 300 grams of the samples in a 600 cc. beaker up to 285 C., holding it at this temperature for 2 hours, and then dethe loss in weight. The first sample loses 4%, the second sample only in weight,

.of gelation, the resin viscosity in' the chart is I expressed in two different ways, first in terms oi the Gardner scale for a solution of parts of resin in 40 parts of xylol, second in terms of am- Drawing It will be seen that the change or viscosity of the resin, measured in solution, the

seed oil drops irom"2*l0 to'--'190..-Normally soluscale of the graph. during the gelation period,

however, it is clearly pictured by the change in the resistance, which the resin offers to agitation, while processed in the kettle. It reaches a high point at about 27 hours. At the same time, the molecular weight has reached a maximum, growing slowly during the upward movement of the viscosity and decreasing again slowly during its downward trend. A temperature of 275. is reached after 24 hours, the high point of 305 is reached after 27 hours, and the kettletemperature is lowered down to 275 again after about 30 hours.

The temperature and time limits given in the two practical cases, described in the previous tabulation and graph, are typical for the process under this invention. Gelation and degelling proceeds above the temperature of 270 and under 325, within about 410 hours.

The formation of copal-like esters in accordance with the present invention involving polymerization first, following by degradation after-,- wards, results in products which present a striking similarity in properties of the new copal-type synthetic resins which closely approach many of the characteristics of the fused natural copals.

The resins of this invention have outstanding solubility both in volatile solvents and oils. In the above tabulation it is shown how solubility is improved for one and the same resin by applying the treatment under this invention. Embracing other resin groups into a comparison of the degree of solubility, the outstanding position of the new resins becomes even more apparent.- Hard and viscous modified phenolic or maleic resins have very limited solubility in kerosene, whereas typical resins of the new class are completely soluble in this solvent. Most phenolics and maleics give clear solutions in bodied oils only at temperatures above 270", whereas the new resins dissolve in oil at temperatures that are 100 lower.

The new resins, furthermore, possess outstanding heat stability with-the result that during the treatment in the varnish kettle they suffer a heat loss which is only a fraction of the loss undergone by other synthetic resins. To cite exact figures a maleic resin may lose 4%, as compared to /2% loss for the resins under this invention, all other conditions being equal.

Due to their process of manufacturing, the new resins possess a high degree of molecular homogeneity. The outstanding internal homogeneity produces mechanical toughness in the resins and also is the reason for the lack of false body. The new resins exhibit genuine viscosity which is not decreased by the heat of varnish cooking, quite in contrast to the false body observed in many high viscosity resins, which are made by polymerization only. Resins with false body are physical mixture of several portions of various degrees of viscosity, ranging from relatively low to very high degrees of polymerization. The actual measured viscosity of such resins is the arithmetical mean of the low viscosity portions and the portions of high viscosity. A part of the latter may be overpolymerized even to a highly gelatinous condition. On further heating of such a resin, either alone or with oil, its gelatinous portion is degelled and liquefied to a more or less fluid state. Thereby the total or average viscosity of the resinas determined by the usual method, is decreased, offering the typical picture of false body. The new resins produced in ac- Due to the fact that the new resins contain free hydroxyl groups they possess high reactivity with fatty acids, a property which is of great practical importance for the varnish maker. Fatty acids are present or formed during the varnish cooking process, especially using soft and slow bodying oils, such as soya oil, linseed oil, and also dehydrated castor oil. Under the same circumstances also fatty carboxyl groups of partially split oils are formed, which act likev fatty acids. The free hydroxyl groups of the. resins under this invention are able to esterify such acidic substances, thereby-producing the linkage of resin and oil. In order to demonstrate this type of resin oil reaction, a representative type of the new resin group produced under the present invention, having an acid value of 5 was heated for 2 hours at 265 C. with the same amount of a linseed oil fatty acid of an acidity of 185. If no reaction took place, the melt would show an acid value of 95, whereas the actual determination shows an acid value of only 50, thereby giving evidence of an avid reaction which has occurred between resin and fatty acids.

As a consequence of resin oil reactivity, the new resins show quick bodying and speedy drying with oils, especially with linseed oil. For the same reason, the varnish films are of outstand-' ing gloss, mechanical toughness, rigidity andresistance quite comparable to those of fossil gum varnishes.

If, as mentioned before, solubiliz ed fossil gums are incorporated into the new resin class, the resin characteristics of outstanding solubility molecular homogeneity, mechanical toughness and heat stability become even more apparent.

The following examples serve to further explain the essential features of the invention and to illustrate them, the parts being by weight unless otherwise indicated;

Example 1. parts of gum rosin are melted.

together with 15.5 parts of maleic anhydride and 22.5 parts of glycerine, which is in excess of the normal amount, and heated up in a way to reach 275 after about 24 hours. On further heating, the batch enters a state of increasing gelation at a temperature of 280. From this point on, applying powerful agitation throughout, the resin is carried through the gelation and degradation cycle by heating it in 4-5 hours to 315-320", and then cooling it rapidly in another 4-5 hours down to 280. During this cycle it first gels and then becomes liquid again and does not finally contain gel particles anymore, when it is unloaded after normal cooling. On the upheat,'slight pressure is applied until the viscosity starts to decrease. On the downheat, vacuum is used until the batch is unloaded.

Analytical details covering the production of this resin are given in the tabulation in column 5 of the specification.

The resulting resin resembles fused copals in appearance and odor, and is distinguished by high solubility in, and reactivity with oils; it is homo geneous in its molecular composition, being free from overpolymerized parts, as well as from por tions of low molecular weight.

this peculiar phenomenon because due to their clear melt is added, at 180, an amount of 25 parts of a condensate made b alkaline condensagradation process technically possible.

tion of one mol para tertiary butyl phenol and two mols formaldehyde in the usual procedure. After the phenol component is absorbed, 15 parts of glycerine are added. This addition includes an excess of several per cent of glycerine over the amount necessary to neutralize the rosin and copal component. The excess is required to supply the free hydroxyl groups, which prevent a solidification of the batch and make the de- For esterification the batch is heated to 275, then heated quickly to 310 and cooled down quickly again,taking,care that the treated resin passes through the temperature range of 280-310 both ways in less than 3 hours. Agitation is applied all the time and vacuum is used on the cooling part of the treatment.

In this way a resin is obtained which possesses high bodying and drying speed, and which in surface coatings develops a toughnessand rigidity, similar to that of fossil gums.

Example 3. 100 parts of gum rosin are heated to 160 C. and, while the resin is-actively agitated, 22 parts of a his phenol-formaldehyde condensate is added slowly. The condensate is produced in' the usual way by combining under the influence of an alkaline catalyst equal weights of his phenol and 37% formaldehyde. After the condensate is dissolved in the rosin, the temperature is raised to 200 and 13.5 parts of glycerine are added, which is considerably more than necessary to simply neutralize the rosin compound, but necessary to prevent solidification of the resinous mass. While the batch is heated up esterification occurs and is practically completed at 275, at a temperature which is reached after about 24 hours. From this point on, with continued agitation, the temperature is quickly raised in 2-3 hours to 305 and cooled rapidly again in 2-3 hours to 275, thereby passing through the period of gelation and degelling within a total time limit of 4-6 hours. When on the downheat 275 is reached,

I vacuum is applied until the temperature has pentaerythritol, and one part of fumaric acid.

The batch is then slowly heated up to an esteriiiis completed, the temperatureis quickly increased to 300, with powerful agitation continuously maintained. As soon as a decrease in viscosity is noticeable, the batch is 'cooled to 270 and held there under vacuum until all volatile matter is removed.

The final resin has the heat stability of a fused copal, with no further heat loss on cooking in the varnish kettle. activity, yielding genuine viscosity with no indication of false body. a

. Having thus set forth my invention, I claim:

1. The method of preparing copal-like resinous esters which comprises depolymerizing a reversible gel resinof a rosin-acid-polyhydric alcohol ester containing free hydroxyl groups, the polyhydric alcohol being selected from the group consisting of glycerine-and the pentaerythritols', said rosin acid-polyhydric alcohol ester being modified by reaction with maleic acid and said reversible gel resin being free from fat acid esters, by heat treatment from just below gelation temperature to the maximum temperature used and from said ness, and heat stability than a polymerized resin of the same chemical composition, melting point and viscosity which has not been depolymerized by the method of claim 1. a

3. The method of claim 1 in which the heating is carried out under pressure until a decrease in viscosity is noted.

4. The method of claim 1 in which the heating is carried out under pressure until a decrease in viscosity is noted followed by application of vacuum to eliminate volatile matter.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,271,804 R001; Feb. 3, 1942 2,283,872

Pratt et al. May 19, 1942 It is outstanding by its oil re- 

